Systems Analysis and Design in a Changing World, sixth edition 5-1
Chapter 5 – Extending the Requirements Models Solutions to End-of-Chapter Problems
Review Questions 1. What are the models that describe use cases in more detail? Fully developed use case description, activity diagrams, and system sequence diagrams.
2. What two UML diagrams are used to model domain classes? Problem domain class diagram and state machine diagram. 3. Which part of a use case description can also be modeled by using an activity diagram? The “flow of activities” section. 4. Explain the difference between a use case and a scenario. Give a specific example of a use case with a few possible scenarios. A use case is the entire function or user goal or event. A scenario is one specific version or instance of that use case. From RMO we have Create customer account as a use case. But we might have Create online Customer account and Create instore customer account and even Create phone customer account as different scenarios. 5. List the parts or compartments of a fully developed use case description. Use case name Scenario Triggering event Brief description Actors Related use cases Stakeholders Preconditions Postconditions Flow of activities Exception conditions
6. Compare/contrast precondition and postcondition. A precondition describes the “states” of data and the system that must exist before the use case can begin. For example to add an item to a shopping cart, the item must exist in the database. A postcondition describes the states of data and the system that must exist after the use case completes. For example after Create a customer account use case, a customer account object (record) must exist.
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7. Compare/contrast postcondition and exception condition. A post condition, as explained about describes states of the data and the system. An exception condition describes some non-normal situation in the processing, i.e. in the flow of activities, that must be handled in some way.. 8. Compare/contrast business process and flow of activities for a use case. Explain how an activity diagram can be used to model both. A business process is larger than a use case. A business process might include various manual business procedures both before and after the “business event” that causes the use case to occur. However, an activity diagram is a powerful model to describe all types of sequences of tasks and activities. The various swimlanes can represent various users or user groups as well as system activities.
9. What is the purpose of an SSD? What symbols are used in an SSD? An SSD (system sequence diagram) is used to describe the messages that flow into and out of a system, i.e. between the system and the use case user. The symbols include: Stick figure for the actor Box with object name for the system object Vertical dashed lines for object lifelines Horizontal arrows for messages Horizontal dashed arrows for return data Comment box for comments
10. What are the steps required to develop an SSD? 1. Identify the input messages (from the activity diagram) 2. Describe the input message using the SSD message syntax 3. Add message conditions such as looping or true/false conditions 4. Add all output message data
11. Write a complete SSD message from the actor to the system, with the actor asking the system to begin the process for updating information about a specific product.
updateProductInformation (productID, updateInformation)
12. What is the name of the sequence diagram symbol used to represent the extension of an object throughout the duration of a use case?
Lifeline or object lifeline
13. What are the two ways to show a returned value on a sequence diagram?
Either with a return value on the left hand side of the equal (:=) sign, or with a return message shown by a dashed line and labeled with the return data.
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14. What are two ways to show repetition on a sequence diagram?
Either with an asterisk on the message label or a loop frame around the message(s).
15. What are the three types of frames used on a sequence diagram?
Loop frame – repeat or loop the contents of the frame Opt frame – send or do not send the message based on true/false condition Alt frame – if-else alternative flows based on condition
16. What is the symbol for a true/false condition on a sequence diagram?
A true/false condition is shown in brackets [ ]
17. What are the parameters of a message?
The parameters represent the input data, i.e. the data that is being passed to the destination object.
18. List the primary steps for developing a SSD.
Ooops, duplicate question. See question 10.
19. What is an object state?
An object state is the state of being of an object, and is usually measured by a set of values. It is comparable to a status condition.
20. What is a state transition?
A state transition is the movement of an object from one state to another state.
21. When considering requirements, states and state transitions are important for understanding which other diagram?
States and Transitions are part of the state machine diagram for an object class. Therefore, they help to understand the objects in the class diagram.
22. What UML diagram is used to show the states and transitions for an object?
States and Transitions are part of the state machine diagram, which describes the activity of the objects in an object class.
23. List the elements that make up a transition description. Which elements are optional?
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Transition-name (parameters, ... ) [guard-condition] / action-expression Any of the three elements may be empty, i.e. are optional.
24. What is a composite state? What is it used for?
A composite state is a high-level state in that it may have other states and transitions inside of it. It is used to represent concurrent states. For example, a printer may be in the “on” state, which is a composite state, and it may be “idle” which is an internal state within “on.”
25. What is meant by the term path?
A path is a sequence of states and transitions. It may be a complete path to describe an entire origin to destination path, or it may be a “snippet” of a path and only contain a few states and transitions.
26. What is the purpose of a guard-condition?
A guard-condition determines whether or not a transition can fire. Usually first the trigger fires to notify the transition that it should execute, but before it begins execution, it tests to see if the guard-condition is true.
27. Identify the models explained in this chapter and their relationship to one another.
The two main models for requirements are the Use case model,which identifies the use cases or the “processes,” and the Domain model class diagram, which identifies the information or data for the system. The Use case diagram is supported by Use Case Descriptions, Activity diagrams, and System Sequence diagrams. The Domain model class diagram is supported by State machine diagrams.
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Problems and Exercises 1. After reading the following narrative, do the following: i. Develop an activity diagram for each scenario. ii. Complete a fully developed use case description for each scenario.
Contractor Sale activity diagram:
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Contractor Sale fully developed use case description:
Use Case Name: Create a new sale Scenario: Create new sale to a contractor (on account sale) Triggering Event: Contractor wants to purchase items. Brief Description: A contractor wants to purchase items. The clerk rings up the items and then adds them to the contractor’s account. Actors: Sales clerk Stakeholders: Sales clerk Accounting department Sales department Preconditions: Customer account must exist. Inventory items must exist. Postconditions: New sale is created. Sales line items are created and connected to the sale. Customer (contractor) account is updated. Flow of Activities: Actor System 1. Clerk enters contractor ID. 1.1 System validates contractor account. 2. Clerk enters each item. 2.1 System finds item in inventory, finds price, adds to 3. Clerk indicates the end of the sale. total. 3.1 System calculates total and 4. If contractor wants receipt, requests adds to contractor account. receipt. 4.1 System prints receipt.
Exception 1.1 If contractor account is out of balance, treat this sale as a cash sale, or Conditions: stop process and send contractor to accounting clerk. 2.1 If system has information missing, sales clerk calls manager and manually enters information. 3.1 If contractor account balance is over the limit, treat as cash sale, cancel, or send contractor to accounting clerk.
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Sale to public activity diagram:
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Sale to public fully developed use case description:
Use Case Name: Create a new sale Scenario: A new cash sale Triggering Event: Cash customer wants to purchase items. Brief Description: A cash customer wants to purchase items. The clerk enters the item ID, and the system creates a sales ticket. Customer pays with cash, check or credit card. Actors: Sales clerk Stakeholders: Sales clerk Accounting department Sales department Preconditions: Inventory items must exist. Postconditions: New sale is created. Sales line items are created and connected to the sale. Payment transaction is created. Flow of Activities: Actor System 1. Clerk starts new cash sale.
2. Clerk enters each item. 2.1 System finds item in inventory, finds price, displays information, adds to total. 3. Clerk indicates the end of the sale. 3.1 System calculates total.
4. Clerk indicates type of payment and 4.1 System processes payment and enters information. creates payment transaction.
Exception 2.1 If system has information missing, sales clerk calls manager and Conditions: manually enters information. 4.1 If customer credit card fails approval, require cash or cancel sale.
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2. Based on the following narrative, develop either an activity diagram or a fully developed description for the use case of Add a new vehicle to an existing policy in a car insurance system.
Problem 7.
Customer Clerk System
H
Provide Policy # Enter Policy # Find policy/ display details
Verify status Provide car details
Enter car information Validate car information against standards for each coverage type
Include coverage type/ select amount Enter coverage information Validate against standards/ add to policy
end for each
Validate combination coverages New driver? yes Invoke Add new driver use case for each additional driver
Provide name and percent Enter name and percent Add driver to car
end for each
Update policy/ H calculater premium/ print statement
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Use Case Name: Add a new vehicle to an existing policy Scenario: Telephone instance with customer and clerk Triggering Event: Customer buys a new vehicle. Brief Description: Customer provides car information, requests coverage with amounts, identifies drivers of the new car. System updates the policy. Actors: Customer service clerk Stakeholders: Customer Customer service department Preconditions: Customer policy must exist and be up to date. StandardVehicle control tables for this vehicle type and year must exist. StandardCoverage tables exist. Postconditions: New vehicle object created and connected to policy. Also connected to StandardVehicle. New coverage objects created and connected to vehicle. Also connected to StandardCoverage. New driver (InsuredPerson) (if necessary) created and added to policy. Existing drivers and percentages updated. Policy updated with new premiums. Flow of Activities: Actor System 1. Clerk enters customer information. 1.1 System finds policy and 2. Clerk verifies policy is current. displays details. 3. Clerk enters car identification 3.1 System validates that car has information. known standard. 4. Clerk enters each type of coverage 4.1 System validates coverage customer requests, including requests. deductibles and coverage amount. 5. Clerk indicates all coverages have 5.1 System does combination been entered. validation on policy. 6. Clerk invokes Add new person use case if necessary. 7. Clerk changes driver percentages on 7.1 System updates driver this car and other cars. information. 8. Clerk indicates everything is 8.1 System updates policy, complete. calculates new premium, prints new statement. Exception 2.1 If policy is not current, clerk requests payment or collects necessary Conditions: information. 3.1 If car type is not in system, clerk refers customer to underwriting to handle this situation. 4.1 If coverage requests are out of range, clerk asks customer for changed amount. 5.1 If some combination is invalid, return to step 4.
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3. Given the following list of classes and associations for the previous car insurance system, list the preconditions and postconditions for the use case Add a new vehicle to an existing policy.
Preconditions: Customer policy must exist and be up to date. StandardVehicle control tables for this vehicle type and year must exist. StandardCoverage tables exist. Postconditions: New vehicle object created and connected to policy. Also connected to StandardVehicle. New coverage objects created and connected to vehicle. Also connected to StandardCoverage. New driver (InsuredPerson) (if necessary) created and added to policy. Existing drivers and percentages updated. Policy updated with new premiums.
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4. Develop an SSD based on the narrative and your activity diagram for problem 1.
Contractor Sale:
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Public sale:
5. Develop a n SSD based on the narrative or your activity diagram for problem 2.
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6. Review the cellular telephone state machine diagram shown in Figure 5-21 and then answer the following questions. (Note that this telephone has characteristics not found in ordinary telephones. Base your answers only on the state machine diagram.) i. What happens to turn on the telephone?
A person has to switch it on with some external event. ii. What states does the telephone go into when it is turned on?
It goes into the composite state (unlabeled, but should have a label of ON). It goes into the Quiet state for one path. It can also go into Charged, Low Warning, or Discharged. iii. What are the three ways the telephone can be turned off?
SwitchOff, Quiet and Low Warning, or Discharged. iv. Can the telephone turn off in the middle of the Active (Talking) state?
Yes, if it is discharged, it leaves the Discharged nested state and the On composite state. v. How can the telephone get to the Active (Talking) state?
Through the origin state of connecting or by answering from the origin state of ringing. vi. Can the telephone be plugged in while someone is talking?
No. The state chart says it can only be plugged in from the Quiet state. vii. Can the telephone change battery states while someone is talking? Explain which movement is allowed and which isn’t allowed.
It can go from Charged to Low Warning and from Low Warning to Discharged. However, because it cannot be plugged in while someone is talking, it cannot move back up from Discharged to Low Warning or Charged. viii. What states are concurrent with what other states? Make a two-column table showing the concurrent states.
Concurrent States Quiet, Dialing, Connecting, Ringing, Charged, Low Warning, Discharged Active, and Plugged In
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7. Based on the following description of a shipment made by Union Parcel Shipments, identify all the states and exit transitions and then develop a state machine diagram.
8. Locate a company in your area that develops software. Consulting companies or companies with a large staff of information systems professionals tend to be more rigorous in their approach to systems development. Set up an interview. Determine the development approaches that the company uses. Many companies still use traditional structured techniques combined with some object-oriented development. In other companies, some projects are structured, whereas other projects are object oriented. Find out what kinds of modeling the company does for requirements specification. Compare your findings with the techniques taught in this chapter.
Answers will vary.
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Solutions to End-of-Chapter Cases
Case Study: TheEyesHaveIt.com Book Exchange For this case, develop these diagrams: 1. A domain model class diagram 2. A list of uses cases and a use case diagram 3. A fully developed description for two use cases: Add a seller and Record a book order 4. An SSD for each of the two use cases in question 3
1. A domain model class diagram
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2. A list of uses cases and a use case diagram
Register
List a book Seller Notify shipment made
Search for book Notify seller about purchase -<
Open account -<
Purchase a book
Enter problem with purchase
Enter satisfaction code
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3. A fully developed description for two use cases: Add a seller and Record a book order
Use Case Name: Register Scenario: Register/add a new seller Triggering Event: A new seller wants to sell books. Brief Description: Seller decides he/she would like to list a book(s). Seller registers and receives a confirmation e-mail. Actors: Seller E-mail server Stakeholders: Preconditions: Seller must not exist in the system. Seller must have all information necessary to register. Postconditions: Seller has an account to list books. Flow of Activities: Actor System 1. Seller connects to EyesHaveIt.com and fills out registration form.
2. Seller submits registration form. 2.1 System notifies seller a confirmation e-mail will be sent. 2.2 System e-mails confirmation of registration to seller. Exception 1.1 If the seller already exists in the system, the system sends prior login Conditions: and password to e-mail address.
2.1 If the seller was removed from the system for bad transactions/credit, the system sends the seller an e-mail notifying the seller of the situation and no account is created.
Use Case Name: Purchase a book Scenario: Purchase a book Triggering Event: A buyer decides to purchase a book from EyesHaveIt.com. Brief Description: Customer searches for a book(s) on EyesHaveIt.com. Customer selects from search results and adds a book(s) to the shopping cart. Customer then proceeds to checkout. If an account exists, the customer confirms purchase, and the system sends a confirmation e-mail to the customer. If an account doesn’t exist, an account is created, the purchase is confirmed, and the confirmation e-mail is sent. Actors: Buyer E-mail server Seller Stakeholders:
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Preconditions: Books and book information must exist in the system. Postconditions: Customer account must exist. Order must be placed. E-mail must be sent to seller. Flow of Activities: Actor System 1. Buyer searches EyesHaveIt.com for 1.1 Searches for all matches a book(s). related to buyer’s search criteria.
2. Buyer selects a book(s) to purchase 2.1 Creates shopping cart. Adds from search results. selected item(s) to the shopping cart.
3. Repeat steps 1 and 2 until all desired books are added to shopping cart.
4. Customer proceeds to checkout by 4.1 Displays list of shopping cart selecting the Checkout button. items for verification.
4a. If customer wishes to remove an 4a.1 Displays list of shopping cart item, he/she selects the item to be items with deleted items removed. removed and then selects the Delete button.
4b. If buyer wishes to add an item, he/she selects the Continue Shopping button and proceeds to steps 1 and 2.
5. Buyer verifies displayed 5. Displays buyer information. information.
6. If information is incorrect or buyer 6.1 Updates new buyer account does not exist, buyer updates information for existing account. displayed information or enters new 6.2 Creates account for new buyer information into the registration form. and sends confirmation.
7. Buyer confirms purchase. 7.1 Records order. 7.2 Sends e-mail to seller. Exception 1.1 If book is sold out, buyer cannot add book to shopping cart. Conditions: 2.1 If buyer account does not exist, a new account must be created. If buyer is rejected for new account based on credit, system sends buyer notification. 3.1 If payment is rejected, system notifies buyer and seller.
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4. An SSD for each of the two use cases in question 3
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Running Cases: Community Board of Realtors
The Multiple Listing Service system has a number of use cases, which you identified in Chapter 3, and three key domain classes, which you identified in Chapter 4: RealEstateOffice, Agent, and Listing.
1. For the use case Add agent to real estate office, write a fully developed use case description and draw an SSD. Review the case materials in previous chapters and recall that the system will need to know which real estate office the agent works for before prompting for agent information.
Use case name: Add agent to real estate office Scenario: MLS clerk adding agent Triggering event: New agent hired in a real estate office Brief description: The correct real estate office is identified, and the new real estate agent information is entered into the system. Actors: MLS clerk Related use cases: Real estate office adds new agent (Web based version scenario) Stakeholders: Real estate office, real estate agent Preconditions: The real estate office must exist Postconditions: Real estate agent is created and associated with real estate office Flow of activities Actor System 1. Find correct real estate office 1.1 Display real estate office information 2. Enter new agent information 2.1 Create new agent record, including with relationship to real estate office
Exception conditions: 1.1 No real estate office found for requested id/name. Display not found message.
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2. For the use case Create new listing, write a fully developed use case description and draw an SSD. Recall that the system needs to know which agent made the listing before the system prompts for listing information.
Use case name: Create a new listing Scenario: MLS clerk creates a new listing Triggering event: New property is put up for sale Brief description: The listing agent is identified and verified. The new property information is entered into the system, along with images etc. Actors: MLS clerk Related use cases: Real estate office/agent creates a new listing (Web version scenario) Stakeholders: Real estate office, Real estate agent, Property owner Preconditions: Real estate office must exist Real estate agent must exist Postconditions: New listing must be created and associated with RE office and RE agent Flow of activities Actor System 1. Find real estate agent 1.1 Display agent and office information 2. Enter new listing information 2. Create new property listing record, associated with agent. Display results.
Exception conditions: 1.1 Agent information not found. Display not found message.
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3. Draw a state machine diagram showing the states and transitions for a Listing object. Note: Answers will vary because students will have to brainstorm valid states for a Listing object. In our solution we will use the following states and exit transitions. (The term “Sale” is used to mean either “Sale” or “Lease”)
State Exit transition For sale Offer to buy Sale pending Close the sale Sold Removed Reinstate listing
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Running Cases: The Spring Breaks 'R' Us Travel Service The Spring Breaks ‘R’ Us Travel Service system has many use cases and domain classes, which you identified in Chapters 3 and 4. Review the domain model class diagram to get a feel for the complexity of some of the use cases.
1. For the use case Book a reservation, write a fully developed use case description and draw an SSD. Review the classes that are associated with a reservation in the domain model to understand the flow of activities and repetition involved. Use case name: Book a reservation Scenario: Book a reservation online Triggering event: Student wants to make a reservation and initiates booking Brief description: Student searches or browses the resorts. He/she checks accommodations and availability. Then he/she makes a reservation for either a single person or a group. (Allow both individual and group reservations.) Actors: Student Related use cases: Create individual account (includes Traveler) Create group account Add person to group (new use case previously undefined) Stakeholders: Student, Resort Preconditions: Traveler and Individual account must exist Group must exist (for group reservation) Resort must exist Postconditions: Reservation must be created and associated with Resort and Group/Traveler Payment must be created and associated with IndividualAccount Flow of activities Actor System 1. Find a resort (search or browse) 1.1 Display resort and accommodation information 2. Check availability of 2.1 Display accommodation accommodations availability information
3. Choose reservation type 4.1 Make reservation 4. Enter reservation details 5.1 Verify individualInfo and 5. Enter reservation payment paymentInfo information Create PaymentTransaction for Reservation Display confirmation Send email confirmation Exception conditions: 5.1 Payment transaction fails
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Note: Based on the requirements of this use case, and the previously defined use cases, the partial domain model class diagram created in Chapter 4 needs to be enhanced with several more classes: Group, Reservation, PaymentTxn, PersonalAccount. The class diagram for Chapter 4 only focused on the social networking part. See the partial class diagram below.
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2. For the use case Add new resort, write a fully developed use case description and draw an SSD. Review the classes that are associated with a resort in the domain model to understand the flow of activities and repetition involved.
Use case name: Add a new resort Scenario: Add a new resort Triggering event: A new resort contracts with SBRU to participate in the vacation program Brief description: A new resort is added with descriptive information. Information about the accommodations available to this program are entered. Information about the facilities available for activities in this program are entered Actors: SBRU clerk, Resort employee Related use cases: Stakeholders: SBRU management, Resort management Preconditions: Resort must not already exist Postconditions: Resort is created Facilities are created and associated with the resort Accommodations are created for this resort Flow of activities Actor System 1. Verify that the resort does not exist 1.1 Check database for resort information 2. Enter resort description 2.1 Create resort record 3. (loop) Enter facilities information 3.1 Create facilities record 4. (loop) Enter accommodations 4.1. Create accommodations record information Exception conditions: 1.1 Resort already exists
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3. Draw an activity diagram to show the flow of activities for the use case Add a new resort. Note: This activity diagram is based on the updated problem domain model.
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4. Draw a state machine diagram showing the state and transitions for a Reservation object.
State Exit transition Open Fulfill reservation, cancel reservation Fulfilled Canceled
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Running Cases: On the Spot Courier Services
1. Based on this description, develop the following for the use case Request a package pickup and for the Web customer scenario: i. A fully developed use case description ii. An activity diagram iii. An SSD
A fully developed use case description Use case name: Request a package pickup Scenario: Web customer requests package pickup Triggering event: Web customer has package(s) to be picked up and requests pickup Brief description: User enters package information (TO address, type of service, size/weight). System returns the cost, expected pickup time, and prints label Actors: Web customer Related use cases: Request package pickup (phone in) Enter package info (pickup package) Stakeholders: Bill, Customer, Delivery employee Preconditions: Customer and customer account must exist Postconditions: Pickup request is created and associated with Customer Flow of activities Actor System 1. For each package 1.1 Enter type of service 1.2 Enter TO information 1.3 Enter package size/weight 1.3.1 Display Cost 1.3.2 Display expected pickup time 1.3.3 Create Request record Create Package record 1.4 Request label print 1.4.1 Print label
Exception conditions: 1.4.1 Label cannot print
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An activity diagram
System sequence diagram
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2. Based on the same description, develop the following for the use case Pickup a package: i. A fully developed use case description ii. An activity diagram iii. System sequence diagram
A fully developed use case description Use case name: Pickup a package (Enter package pickup information) Scenario: Delivery employee picks up package Triggering event: Delivery employee arrives at customer's location and picks up a package Brief description: Delivery employee verifies package with pickup request information, OR enters new package information. If cash customer, process payment. Actors: Driver Related use cases: Create customer and customer account Accept payment Scan package (movement) Stakeholders: Customer, Driver, Bill Preconditions: Customer should exist (else invoke Create customer use case) Postconditions: Create package record and connect with Customer, PickupRequest, Movement event Flow of activities Actor System 1. If package has NO label, search for 1.1 Access pickup info, update request by Customer name package
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If no pickup info, display none
2. If pickup request not found, enter 2.1 Process new package info new package info 3. Request print label 3.1Print label 4. Scan package label 4.1 Update pickup request, package Create pickup MovementEvent 5. If cash customer, enter payment info 5.1 Process payment Exception conditions: 5.1 Invalid payment data
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An activity diagram
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A system sequence diagram.
3. Develop a state machine diagram describing all the possible status conditions for a Package object. State Exit transition Pending pickup packagePickup ( ) Picked up arriveAtWarehouse ( ) At warehouse loadedOnDeliveryTruck ( ) Out for delivery delivered ( ) Delivered none Lost found ( )
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Running Cases: Sandia Medical Devices Figure 5-22 shows a set of use cases for the patient and physician actors. Answer the following questions and/or complete the following exercises:
1. Which use cases include which other use cases? Modify the diagram to incorporate included relationships.
2. Consider the use cases View/respond to alert and View history. Both actors share the latter, but each has a different version of the former. Why do the actors have different versions of the
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View/respond to alert use case? Would the diagram be incorrect if each actor had his own version of the View history use case? Why or why not? View/respond to alert: Even though the names are the same, the detail steps might be very different. It would be possible to make them different scenarios of the same use case. But making them separate use cases also works since the actors are different, the steps are different, and the system responses are different. View history: View history does the same activities no matter who the actor is. In this case it would not make sense to have separate use cases since the processing steps, the data, the activities are both the same.
3. Develop an SSD for the View history use case. Assume that the system will automatically display the most recent glucose level, which is updated at five-minute intervals by default. Assume further that the user can ask the system to view glucose levels during a user-specified time period and that the levels can be displayed in tabular form or as a graph.